import numpy as np
# 用numpy创建一个一维数组
arr = np.array([1,2,3,4,5]) 
print(arr)
# numpy创建一个二维数组
arr = np.array([[1,2,3,4,5],
                [5,6,7,8,9]])
print(arr)
# numpy计算矩阵乘法    
a = np.array([[1,2,3],
              [2,3,4],
              [3,4,5]])
b = np.array([[1,2,3],
              [2,3,4],
              [3,4,5]])
c = np.dot(a,b)
c = a @ b
print(c)
# 计算向量内积
a = np.array([1,2,3])
b = np.array([2,3,4])
# c = np.dot(a,b)
c = a @ b
print(c)